GEM: Numerical Modeling of Ultra-Low-Frequency (ULF) Waves and the Production of Geomagntically Induced Currents

GEM：超低频 (ULF) 波的数值模拟和地磁感应电流的产生

• 批准号: 2225270
• 负责人: Robert Lysak
• 金额: $ 47.8万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-12-01 至 2025-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2225270&HistoricalAwards=false
• 关键词: GEM; Numerical; Modeling; Ultra; Low

The magnetic field of the Earth is not static and is constantly fluctuating. Magnetic field lines can, in some sense, be thought of like strings on a musical instrument, like a guitar or harp. Just like the strings of a harp, these field lines are of different lengths and have different densities, so each field line fluctuates at its own frequency. In addition, the region around the Earth can also act as one of a set of kettle drums that also have their own frequency. These fluctuations give rise to electrical currents that flow through space and can often flow on and beneath the surface of the Earth. These currents can have important effects, such as disruptions in the power grid and corrosion of oil and gas pipelines. A computer model was developed to describe the currents flowing in space and their effect on ground currents. The proposed work will further improve this model by including more realistic conditions based on statistical models and satellite measurements of the density of particles in space. This work will also support a graduate student who will learn more about computer simulation as well as the issues.Ultra-low-frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. The primary goal of the proposed research is to extend our models of these waves and to apply these models to better understand the structure of ULF waves in a more realistic magnetosphere and to relate observations in space and on the ground, particularly regarding the excitation of geomagnetically induced currents (GICs). In previous work, the proposers have developed a three-dimensional numerical model in dipole geometry to describe the propagation of ULF waves in the inner magnetosphere. They have also developed a similar code in spherical geometry that covers all latitudes. A major task will be to integrate the dipole code and the spherical code. The proposers will base the underlying density structure in the inner magnetosphere on empirical models of the ionosphere and plasmasphere. The model results will be compared with data from the Van Allen Probes and other platforms in space, as well as with observations from ground magnetometers. This project will investigate the response of the magnetosphere-ionosphere coupling system to external perturbations, such as the interaction of the magnetosphere with interplanetary shocks with the perturbations induced during substorms. The proposers will also investigate the excitation of geomagnetically induced currents (GICs) on the ground by extending the model from the ionosphere through to the ground.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球的磁场并不是静态的，而且是不断波动的。在某种意义上，磁力线可以被认为是乐器上的弦，就像吉他或竖琴。就像竖琴的弦一样，这些场线的长度不同，密度也不同，所以每条场线都有自己的频率波动。此外，地球周围的区域也可以充当一组壶鼓中的一个，这些壶鼓也有自己的频率。这些波动产生了流经太空的电流，通常可以在地球表面上和下面流动。这些电流可能会产生重要影响，例如电网中断和石油和天然气管道的腐蚀。开发了一个计算机模型来描述空间中流动的电流及其对地面电流的影响。拟议的工作将通过纳入基于统计模型和卫星测量的空间粒子密度的更现实的条件，进一步改进这一模型。这项工作还将支持一名研究生，他将学习更多关于计算机模拟以及这些问题的知识。超低频波在磁层近地区域的能量传输中发挥着重要作用。拟议研究的主要目标是扩展我们对这些波的模型，并应用这些模型来更好地理解更真实磁层中的超低频波的结构，并将空间和地面观测结果联系起来，特别是关于地磁感应电流(GIC)的激发。在以前的工作中，提出者发展了一个偶极子几何的三维数值模型来描述超低频波在内磁层中的传播。他们还在球面几何中开发了一种覆盖所有纬度的类似代码。一项主要任务将是整合偶极子代码和球面代码。提出者将以电离层和等离子体层的经验模型为基础，建立内部磁层的基本密度结构。模型的结果将与范艾伦探测器和其他太空平台的数据进行比较，并与地面磁强计的观测结果进行比较。该项目将调查磁层-电离层耦合系统对外部扰动的反应，例如磁层与行星际冲击与亚暴期间引起的扰动的相互作用。提出者还将通过将模型从电离层延伸到地面来调查地面地磁感应电流(GIC)的激发。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。